1. Field of the Invention
This invention relates generally to compositions, methods and apparatus for use in the manufacture of semiconductor, photovoltaic, LCD-TFT, or flat panel type devices. More specifically, the invention relates to methods and compositions for depositing alkali earth metal thin films, with superconductive or magnetoresistance properties, on a substrate.
2. Background of the Invention
As the design and manufacturing of semiconductor devices continues to evolve, the semiconductor industry is constantly seeking new and novel methods of depositing films onto substrates, such that the resulting film will have certain sought after properties. Two such examples of sought after properties are films which exhibit superconductive-like or magnetoresistance properties. Field effect transistors (FET) with a semiconductor channel make use of an oxide superconductor material in the gate electrode, which can provide control of parasitic resistance, capacitance, and a proper work function when operated at an adequate temperature. Magnetoresistance materials are used in hard drive applications, and allow for better density and capacity of storage in the resultant devices.
Films utilizing calcium and strontium, especially such films with a perovskite-type structure, have been examined for these superconductive and magnetoresistance applications. Some of the structures which have shown promise for these applications include: CaCu3Ti4O12; CaTiO3; (PrCa)MnO3; (Ca, Mn,Sr)RuO3; ZrO2—CaO—ZrO2; HfO2—CaO—HfO2; Ca:ZrO2; Ca:HfO2; Ca:Ln2O3.
In the case of calcium/hafnium structures, because of its ability to form solid solutions and ternary crystalline phases, calcium oxide is an appropriate additive to HfO2. Stoichiometric compounds with low defects should form relatively easily, compared to mixtures of Al2O3 and HfO2. CaO has a wide band gap (6.8 eV), which might be suitable in dielectric stacks with HfO2 for instance.
With its perovskite structure, CaHfO3 has been considered as an interesting material for gate capacitor dielectric in metal-oxide-semiconductor field-effect-transistor (MOSFET) with Si or SrTiO3 channels.
Calcium oxide films have been obtained by atomic layer deposition (ALD) process using calcium β-diketonate, O2 and ozone. The material first formed was calcium carbonate which turned into CaO after heat treatment at 670° C. in CO2-free atmosphere.
Consequently, there exists a need for methods and materials to deposit thing films containing calcium and strontium.